This invention relates to a clutch apparatus and particularly concerns a positively shifted clutch apparatus for marine propulsion engines.
Clutch mechanisms have been employed for selectively connecting a drive gear and a driven gear to establish one of two opposite rotating outputs. In marine outboard engines, the lower gear case includes a propeller shaft. A pair of axially spaced driven bevel gears are rotatably mounted on the shaft and coupled to a drive bevel gear connected by a drive shaft to the internal combustion engine. The driven bevel gears are oppositely rotated. A clutch mechanism which includes a movable clutch collar is mounted on and coupled to the shaft by a pin and slot connection between the driven bevel gears. The clutch collar is movable between a neutral position, a forward position and a reverse position. The opposite faces of the clutch collar and the opposed faces of the bevel gears are formed with complementing positive engaging clutch teeth or jaws for positive coupling of the driven gears to the shaft. The clutch collar is generally spring-loaded to the forward drive position. It is connected through a coaxial shift rod to a rotating cam mounted in the forward end of the gear case and actuated by a vertical shift shaft to position the clutch collar against the spring loading of the collar. The spring thus forms the actuating force on the collar when shifting from reverse to neutral to forward shift positions. Generally, the clutch jaws of the clutch collar and reverse driven gear are formed with a positive angle drive face to create a disengaging force component of the driving force transmitted through the clutch jaws. The positive angle construction thus assists the spring in overcoming the friction at the driving jaw faces when shifting from reverse, and thereby permits shifting to neutral. However, the required positive angle structure creates a relatively heavy loading of the cam and cam shift rod with a corresponding wear of the components. The worn components result in mislocation of the clutch collar and prevent proper shifting into reverse. Further, the forward gear and collar jaws are required to have a negative angle driving jaw face which assists the spring in holding the forward jaws engaged. The heavy loading provided by the positive and negative jaw angles also require substantial shift operating forces in shifting.